In the manufacture of labels, tags, tickets and the like, it is now common practice to carry out at least part of the conversion operations with a diecutting roll, acting upon traveling web stock. This is done, for example, to cut holes or slots of various shapes in the web, or to form fastener openings, corners or necked-in areas in the finished article. However, serious problems must be dealt with in carrying out such operations, which arise primarily as a result of the accumulation of scrap material within the die element, and/or the inefficient removal of the scrap from the web.
As will be readily appreciated, by cutting through the entire thickness of the web stock the scrap can normally be stripped away, simply by virtue of its frictional engagement within the die cavity. In the absence of some provision for removing the scrap from the cavity, however, accumulations therein will quickly render the roll ineffective, and may often cause severe damage, such as bursting of the die formations provided thereon. These problems tend to be particularly acute when the web stock is printed or carries an adhesive coating.
Diecutting rolls are disclosed in the art which utilize positive and/or negative air pressure to efficiently remove scrap pieces from the cutting element. An assembly that is particularly effective, which operates on an air-ejection principle, is described and claimed in Kesten et al U.S. Pat. No. 3,698,271. A suction unit is taught by Buck et al, in U.S. Pat. No. 3,194,095, for continuously withdrawing confetti produced in the manufacture of indexing holes in paper forms, using a pair of rotating punch dies; and a "push-pull" chip removal system is disclosed by Stoop, in U.S. Pat. No. 3,680,419.
Although highly desirable in many applications, apparatus that relies upon air pressure to remove and control the disposition of scrap is not ideal in all instances. Pneumatic effects are simply not as positive as might always be desired for effecting the discharge of scrap from a die, and there is of course a certain amount of complexity involved in the associated air-delivery system.
It is also common practice to rely upon mechanical means to assist in the stripping of scrap from web stock. In the apparatus of Huck U.S. Pat. No. 3,174,428, for example, the perforating pins of a male die cylinder enter related die holes of a female cylinder. Similarly, in accordance with Danti U.S. Pat. No. 4,220,272, the apparatus provided includes a break-out punch, for removing precut scrap pieces, which intersects the scrap-removal path; at the upstream scoring station, rolls with precisely aligned punches are used to cut partially through the thickness of the web from both sides, leaving a weak section about the entire periphery of the scrap piece by which it is carried to the knock-out station.
Systems have heretofore been made available commercially which consist of two diecutting rolls operated in tandem to produce openings in traveling web stock; i.e., each die cuts only a portion of the periphery, with the complete score being made by coaction of the pair. The air-eject principle of the above-identified Kesten et al patent was used in one instance to effect removal of scrap from the downstream roll.
Despite the activity in the art exemplified by the foregoing, a demand nevertheless remains for a system by which disposal of scrap pieces, produced by rotary diecutting of web stock, can be achieved in a positive, highly reliable, and yet relatively simple manner.
Accordingly, it is the broad object of the present invention to provide a novel system of tandem diecutting rolls for producing openings in traveling web stock, in which disposal of the scrap generated is achieved in a highly effective and efficient manner.
It is a more specific object of the invention to provide such a system in which the scrap is mechanically removed from the die formations of the final cutting roll, positively and with a high degree of reliability.
Corresponding broad and specific objects concern the provision of a novel diecutting press and novel method, incorporating the foregoing system and the mode of operation that it affords.
Additional objects of the invention are to provide such a system, press and method, which are relatively uncomplicated, economical, and facile to use and to carry out.